This invention relates to impulse ink jet devices and ink supply systems for such devices.
Impulse ink jet devices which provide a drop on demand in response to the state of energization of a transducer are typically supplied with ink from relatively small cartridges since the volume of ink consumed in an impulse ink jet device is relatively small as a normal rule. However, certain industrial applications of impulse ink jet devices require large volumes of ink over extended periods of time. For example, on-line printing of corrugated containers may require a plurality of ink jet print heads where each head comprises a large number of jets so as to produce relatively large characters and/or bar codes. Under these circumstances, a large volume of ink is used for extended periods of time. The use of small cartridges becomes impractical. For printing in this type of application, a relatively large ink supply is necessary, e.g., a container holding 125, 250, 500 or 1000 milliliter. The use of such a large ink supply does however pose certain problems for an impulse ink jet apparatus.
First, an impulse ink jet apparatus must be primed properly with ink in order to operate properly. Priming of an impulse ink jet requires that positive pressure be generated in connection with the supply of ink so as to force the ink through the ink jet chambers and the orifices of the ink jet while preventing the sucking of ink back through the orifices and the chambers upon completion of priming. One possibility for priming involves a bottle squeezing technique with some relief of the built-up pressure through the use of various types of valves including umbrella, duck bill and flapper valves. Such valves are required to be sensitive to back pressure while being strong enough to seal ink in during the squeezing phase. In addition, such valves may present problems of material compatibility with the inks used. Accordingly, it may be difficult to reliably design to meet the above-stated criteria. Another possibility includes a manually operated valve but this requires precisely timed manual procedures which may pose difficulties to operators in the field.
Priming of an impulse ink jet system may also be accomplished by pressurizing an air space above an ink reservoir. However, any increase in ink pressure in a container in which the ink reservoir is located will continue to force ink out through the ink jet device even after the pressure is removed. The device may therefore xe2x80x9cweepxe2x80x9d uncontrollably. Pressure could be applied directly to the container by puncturing a hole in the container in the air space above the ink which may also be used so as to relieve pressure within the container as soon as the pressure is removed from the container. This option, however, makes removal of partially filled containers messy as well as foreclosing on ecologically sound refilling policy.
Peristaltic pumps have been proposed for use in priming impulse ink jet apparatus wherein rollers are moved into contact with a tube containing ink, rolled along the tube containing ink and then separated from the tube so as to allow the free flow of ink through the tube. Such a mechanism is complex, expensive and may be difficult to implement in a variety of applications.
It is an object of this invention to provide a large ink supply for an impulse ink jet device.
It is a further object of this invention to provide a priming mechanism for a large ink supply used in an impulse jet system which is reliable, easy to use and poses no material compatibility problems.
It is a further object of this invention to provide an ink supply system and an associated priming mechanism which is ecologically sound.
It is a still further object of this invention to provide an ink supply and associated priming mechanism which does not cause weeping from the head at the conclusion of priming.
It is a still further object of this invention to provide an ink supply and associated priming mechanism which substantially eliminates the possibility of any spillage of ink.
It is a still further object of this invention to provide a priming mechanism which imposes the minimum of constraints on the remainder of the system.
In accordance with these and other objects of the invention, a preferred embodiment of the invention comprises an impulse ink jet apparatus including an impulse ink jet head, a supply base comprising a reservoir for ink and adapted to receive an ink supply and means for coupling the ink jet head to the supply base.
In accordance with one important aspect of the invention, means for coupling the impulse ink jet head to the supply base includes a flexible tube which is coupled to a hand actuated peristaltic pumping device comprising a support surface in contact with and supporting the tube, a squeezing surface adapted to contact and squeeze the tube against the support surface and means for moving the squeezing surface relative to the support surface through a peristaltic pumping orbit. The orbit includes movement from a static position in the absence of a hand gripping force with no contact between the squeezing surface and the support surface to a position of contact between the squeezing surface and the tube in the presence of a hand gripping force. Such movement is followed by movement between the support surface and the squeezing surface in one direction while the squeezing surface is in contact with the tube during continued application of the hand gripping force so as to force ink through the tube in a peristaltic pumping stroke followed by movement between the support surface and a squeezing surface in the return stroke so as to return the squeezing surface to the static position in the absence of a hand gripping force with no contact between the squeezing surface and the tube. The squeezing surface comprises a roller and the support surface is arcuate with the angle of attack between the squeezing surface and the support surface being not more than 45xc2x0.
In accordance with another important aspect of the invention, the ink supply comprises a container for storing ink jet ink having an opening for releasing ink from the container and a valve member mounted in the opening in the container and spring means coupled to the valve member for biasing the valve member so as to prevent the flow of ink from the container when the ink supply is not mounted on the supply base.
In a preferred embodiment of the invention, the container comprises a bottle portion, a cap portion and a valve enclosure located within the cap portion for enclosing the spring means and a portion of the valve member. Preferably, the cap portion includes threads and the bottle portion includes threads which are mutually engaged. The actuating surface of the valve means is exposed through the opening of the container and is preferably concave so as to receive actuating means mounted on the supply base.